1896. ] MYOLOGY OF RODENTS. 169 
ligament was seen in Rhizomys running from the axillary border 
of the scapula, between the origins of the teres major and minor, 
across the latter muscle to the metacromion process. A similar 
ligament has already been described in Lagostomus ’. 
Biceps Cubiti.—Yhere can be no doubt that, speaking generally, 
one of the characteristics of the Myomorpha is a double-headed 
biceps. This was noticed in every specimen which I dissected. 
Milne-Edwards, however, found only one head in Siphneus, but it 
is possible that further investigation may prove that this was 
merely an individual variation. In Hydromys Windle does not 
notice the condition of the biceps. 
As a rule the insertion is into both bones of the forearm, but in 
Cricetus and Myoxvus the muscle only goes to the radius, while in 
Rhizomys the ulna is the only bone to which it is attached. In 
Georychus and Bathyergus the two heads are easily separable 
down to the insertion by a little force. In the former the coracoid 
head goes entirely to the radius, the glenoid head to the radius 
and ulna; inthe latter both heads can be traced to both bones. 
Coraco-brachialis—In the Myomorpha the most usual arrange- 
ment is to find the second and third parts, described by Wood’, 
present; they are, however, fused, and the muscle has one 
continuous insertion from the middle of the humerus to the 
internal condyle. This description applies to Rhizomys, Siphneus, 
Microtus, Myodes, Heteromys, Hydromys, and the Murine. The 
Cricetine (Cricetus and Cricetomys) have the same arrangement, 
but in addition the first part or rotator humeri is present. In 
Gerbillus and Myowus only the second part was seen. 
In Georychus the muscle was absent, while in Bathyergus it 
was very small, and was only represented by the second part. 
Milne-Edwards says that the muscle is absent in “le Rat-Taupe 
du Cap,” by which, 1 suppose, Bathyergus is meant. In all the 
animals dissected, as in other Rodents, the musculo-cutaneous 
nerve passes above the second part of the muscle. 
_ _Brachialis Anticus.— All the Myomorpha have the external and 
internal heads of the brachialis anticus, and these are more or 
less completely fused; perhaps Bathyergus shows them most 
clearly separated from one another. The insertion, in every case 
that I dissected, was into the ulna only, but Milne-Edwards 
describes an additional feeble attachment into the head of the 
radius in Siphneus. 
Triceps and Anconeus.—There is no difference between the 
Myomorphine triceps and that of other Rodents. In Cricetomys 
it was noticed that the outer head was inserted largely into the 
fascia of the outer side of the forearm. Bathyergus resembles 
Castor in the great development of the muscle, and in the fact 
that it is attached to both sides of the olecranon, as well as to the 
top. The anconeus has the usual attachments, and shows nothing 
of special interest. 
1 Pp. ZS. 1894, p. 263. 
2 Journ. of Anat. vol. i. p. 45. 
